50 
F. IV. Oliver. 
pinnules. In this writer’s figure of a section parallel to the surface 
of a pinnule the pockets shew an oval outline, they are slightly 
variable in size, and contain numerous small spore-like bodies. 
A comparison of the similar preparation represented here (PI. iv., 
fig. 1 ) with Renault’s fig. 10, will shew the identity of the structures. 
In his comments on their nature Renault refers in the most guarded 
terms to the possibility that these pockets might be the sporangia 
of Alethopteris. On the whole he would seem to have been 
impressed with the resemblance which they present to Excipulites 
callipteridis of Schimper . 1 
The specimens under consideration afford some additional 
features worth recording. The irregular distribution of the pockets 
finds confirmation in the cross sections of pinnules represented in 
figs. 2 and 3. In the former figure, which represents part of the 
lamina of a pinnule in transverse section (the midrib being on the 
extreme right of the figure), four of these pockets (a, b, c, d) are 
shewn lying in the areas of spongy parenchyma which alternate 
with the exarch bundles of the pinnule. They are closely approximated 
to the lower surface of the leaf which projects slightly in the form 
of convex blisters owing to the displacement due to the pockets. 
Another pinnule in transverse section is shewn in fig. 3 with two 
pockets (a and b), one close to the midrib, the other in the angle 
formed by the infolding of the rolled margin. These two pockets, like 
n and d in fig. 2 , appear to have been cut in the middle plane and 
shew an ostiole-like aperture through which the contained spores 
were probably discharged. The wall of the pocket is badly defined. 
It is dark in colour and under a high magnification shews an obscure 
stratification (fig. 4). The appearance certainly suggests that this wall 
may owe its origin to the flattening of the neighbouring parenchyma 
cells of the leaf, a result of the expansion of the pocket. The 
small contained spores are not quite spherical, their longer diameter 
averages about 16//,. The wall of the spore is covered externally by 
numerous tiny rugosities, as represented in fig. 5. The general 
facts of their structure and distribution seem consistent with the 
view that these pockets are the fructifications of a parasitic fungus. 
Superficially they recall a minute Pyrenomycete, but no useful 
purpose would be served by a discussion of its possible affinities. 
The manner of origination of the spores in the pockets is quite an 
open question. A portion of the wall of a pocket together with 
some of the adjacent spores are represented in fig. 4. The details 
’See Scliimper, Traite d. paleont. vegrt., Vol. I., p. 142 and PI. 
xxxii., figs. 6 and 7 . 
